The present invention relates to an apparatus and method for cleaning recorded discs and particularly to an apparatus and method for washing contaminating materials from the surfaces of the discs.
Recorded discs generally comprise a circular flat plate or disc of a plastic material having a center hole therethrough and recorded information provided thereon in the form of a surface relief pattern formed along a spiral path in the major surfaces of the disc. The surface relief patterns preferably are formed in a spiral groove in the surfaces of the disc. Recently there has been developed a high density recorded disc, such as a video disc, in which there ae a large number of grooves per inch of the diameter of the disc, e.g. 10,000 grooves per inch (4000 grooves per cm). Because of the large number of these grooves, they are very narrow and shallow, i.e. 2.7 microns in width and 4000 Angstroms in depth. Because of the fineness of these grooves, any contaminants, such as dirt, dust or other foreign particles, can severely disrupt the operation of the disc and their presence is therefore highly undesirable.
In order to remove contaminants from the surface of the discs, there has been developed a process wherein the discs are immersed in a cleaning solution, such as an aqueous solution of organic alcohol and amines of the type commercially available as 1160B from the Shipley Company, which removes the contaminants. The discs are then rinsed in water to remove the cleaning solution. To insure complete removal of the cleaning solution and contaminants, the discs are rinsed in several baths of the water, for example three baths. The first bath removes most of the cleaning solution, the second bath removes some of the remaining cleaning solution, and the final bath removes the remainder of the cleaning solution. Thus, the first bath becomes the dirtiest, containing a large amount of the removed cleaning solution and organic contaminants from the disc surface, the second bath is cleaner, and the third bath is the cleanest. To maintain this condition of the water baths, the water from the third bath overflows into the second bath and the water from the second bath overflows into the first bath. However, it has been found that the removed cleaning solution and disc material that is leached from its surface by water have a tendency to float to the surface of the baths and form a film thereof on the surface of the baths. Thus, when the discs are lifted out of the bath, some of the film will stick to the surfaces of the disc and recontaminate the discs. Therefore, it is desirable to have a rinsing bath in which the discs will not be recontaminated when removed from the bath.